In recent years, a metal oxide thin film transistor attaches more and more attention since its advantage of high mobility, good transparency, stable thin film structure, the low manufacturing temperature and low cost. Especially the indium gallium zinc oxide, In—Ga—Zn—O, IGZO as the representative of the metal oxide TFT, with high compatibility with the currently manufacturing process of the a-Si TFT, thereby obtaining a wide range of applications of the manufacturing the large size OLED panel.
The method of manufacturing thin film transistor in conventional includes four mask steps, namely:
forming a gate electrode on a substrate by using the first mask;
forming an active layer pattern by using the second mask;
forming an etching stop layer pattern by using the third mask; and
forming a drain electrode and a source electrode patterns by using the fourth mask.
Therefore, how to save costs of the mask and simplify the process is the issues for continued research in the industry.